As a note: 2 quarts is approximately 36 spheres
Recommended minimum usage is approximately 1 quart per 100 gallons of tank water.

This means 18 spheres for 100 gallons, 9 for 50 gallons, so on an so forth. Does this means this is ALL I'll need for bio filtration? So if I have a 18 gallon tank, adding 3-4 spheres is all I'll need for biochemical? Wow!